Review of allanite:Properties,occurrence and mineral processing technologies

Allanite is commonly encountered as an accessory rare-earth silicate mineral in association with minerals such as garnet,biotite,and feldspar.It is distributed globally and occurs in igneous formations such as granites,pegmatites,and syenites,as well as in various metamorphic rocks such as schist,gneiss,and amphibolite.Moreover,it can be found in mineral veins formed through hydrothermal activity.While allanite has not yet been extensively utilized for the production of rare-earth elements,recent discoveries of high-grade rare-earth-rich allanite deposits in Wyoming,USA,highlight its economic potential.However,despite ongoing research on the mineralogy and processing of rare-earth minerals,allanite has not received widespread attention in mineral processing.To achieve economical extraction of rare-earth elements from allanite in the future,systematic studies on processing techniques(e.g.,density separation,magnetic separation,flotation,leaching)are imperative to fully unlock the potential of allanite as a rare-earth element source.To pave the way for future investigation of allanite and address the unique processing challenges,this review article aims to comprehensively summarize previous studies,encompassing properties,occurrences,and processing technologies ofallanite.